This invention relates to cryptographic systems, and more particularly, to cryptographic systems using derived keys.
It is often desirable to encrypt sensitive electronic communications such as email messages.
With public key cryptographic systems, two types of keys are used—public keys and private keys. Senders may encrypt messages using the public keys of recipients. Each recipient has a private key that is used to decrypt the messages for that recipient.
With symmetric key cryptographic arrangements, the sender of a message uses the same key to encrypt the message that the recipient of the message uses to decrypt the message. An advantage of symmetric key cryptography is that symmetric key encryption and decryption algorithms are computationally efficient.
Often senders and recipients of secure messages have existing relationships with organizations. For example, a bank may wish to send its customers account statements securely. As another example, a customer who receives an encrypted account statement may wish to send a secure email message back to the bank to ask a question.
It is an object of the present invention to provide secure messaging systems that use symmetric keys to facilitate secure communications.